Divergent selection for intramuscular fat content in rabbits. II. Correlated responses on carcass and meat quality traits

Correlated responses on carcass and meat quality characteristics after 3 generations of divergent selection for intramuscular fat (IMF) content were assessed by comparing the high and low lines. Selection was based on the phenotypic value of IMF content of LM, measured in 2 full sibs of the first parity. Traits measured were: BW, HCW, commercial carcass weight (CCW), reference carcass weight (RCW), scapular (SF) and perirenal fat (PF) content, meat-to-bone ratio (M: B) of the hind leg, pH of LM, color (lightness, L*; redness, a*; and yellowness, b*) of the carcass and of a LM section, protein content, and fatty acid (FA) composition of LM. A total of 174 records was used to estimate the correlated selection response. Data were analyzed using Bayesian methodology. We considered one-third of the phenotypic SD of a trait as a relevant value for the difference between lines. Then, the probability of the difference being greater than a relevant value (P-R) was calculated. A low P-R implies that the lines compared are similar. Carcass weights (P-R between 0.24 and 0.31) and M: B of the hind leg (P-R = 0.15) were not modified by selection for IMF content. There was a slight negative correlated response for BW, although evidence of its relevance was low (P-R = 0.48). Scapular fat content was similar between lines (P-R = 0.03). There were differences for PF content, although there was low evidence for showing its relevance (P-R = 0.47). Color traits of the carcass were not affected by selection (P-R between 0.04 and 0.30). In muscle, L* was also similar between lines (P-R = 0.26). There were differences for a* and b*, although there was little evidence of their relevance (P-R = 0.35 and 0.40, respectively). There was a positive correlated response on muscle pH and differences could be relevant (P-R = 0.77). Protein content of LM was similar between lines (P-R = 0.13), whereas FA composition was affected by selection. There were relevant differences between lines for MUFA (P-R = 0.99), n-3 (P-R = 0.95), and n-6 (P-R = 0.98) percentages. For individual FA, differences were relevant for C18: 1n-9 (P-R = 0.97) and C20: 5 n-3 (P-R = 0.98). In conclusion, selection for IMF content may modify carcass quality by increasing PF content. Moreover, it led to some modifications in pH and FA composition of LM.